Pulse receiving circuit



June 28, 1949. cABEs PULSE RECEIVING CIRCUIT 3 Sheets-Sheet 1 Filed Jan. 22, 1943 wi l:

INVENTOR L CARES ATTORNEY June 28, 1949. CABES 2,474,220

' 1 PULSE RECEIVING CIRCUIT v Filed Jan. 22, 1945 3 Sheets-Sheet 2 e, A if:

I i- U 7 15 2" INVENTOR LCABES June 28, 1949. L. CABES PULSE RECEIVING CIRCUIT Filed Jan. 22, 1943 3 Sheets-Sheet 3 Patented June 28, 1949 UNITED 2,474,2Zii

STATES PATENT OFFICE PULSE RECEIVING CIRCUIT Application January 22, 1943, Serial No. 473,272 In the Netherlands July 11, 1941 10 Claims. 1

The invention relates to signal transmission systems, and more particularly to pulse receiving circuits.

Heretofore, in carrier wave pulse receiving circuits it has been the practice, either to impress the rectified modulated carrier wave, through an appropriate filter and transformer, directly upon a stepping relay, or to apply the carrier wave through a suitable transformer to the grid of a hot cathode vacuum tube, in the plate circuit of which the stepping relay was inserted.

Both these methods present, however, certain disadvantages and one object of this invention is to afford improved modulated carrier wave pulsereceiving circuits.

One feature of the invention is the use of a pair of cold-cathode tubes as relay control means in a signal receiving circuit.

Another feature of the invention is the use of a single carrier wave frequency for lighting temporarily and alternately the two cold cathode tubes, one being lit during the presence of the signaling current and the other during the absence of the signaling current.

Fig. 1 shows a simple embodiment of the invention, illustrating the principles of operation thereof;

Figs. 2 and 3 show different embodiments utilizing the basic principles of the invention, each embodiment presenting certain individual advantages;

Fig. 4. illustrates further application of this invention, in the form of an impulse corrector; and

Fig. 5 shows a complete circuit for applying this invention to a telephone or similar system for the establishing of connections, in the form of a dial impulse receiving device.

In Fig. 1 the incoming signaling line is terminated in a transformer T, the secondary winding of which is connected to a, circuit, comprising rectifier R, condensers C1 and C2, resistances r1, r2, rs and n, a potentiometer P and energizing battery therefor, a stepping relay Sr and two cold cathode tubes L1 and L2. The function of these various elements will be clear from the following description thereof.

The cold cathode tube referred to is of the well known type, which requires a specific control gap breakdown potential Vx to light the control gap between the two electrodes e1 and 62, Whereas a substantially higher main gap breakdown potential Vy is required to light the main gap between the anode A and either of the two electrodes e1 and (22. Once the control gap has been lit, however, a sustaining potential V2, which may be considerably lower than Vy, is sufficient to maintain a current in the main gap.

It will be seen from Fig. 1 that the control electrodes of tube L1 are connected to two points, Z and B, of the potentiometer P. The potential difference between points Z and B is less than the control gap breakdown voltage, so that the tube L1 remains normally extinguished.-

It will also be seen from Fig. 1 that the control electrodes of tube L2 are connected to points Z and C of the potentiometer. The potential difference between points Z and C is greater than the control gap breakdown voltage, so that normally tube L2 is lit. This is indicated in the figure by cross-hatching the tube L2.

In order to get a clearer idea of the operation of the two tubes, the action of an incoming alternating current will be analysed on the assumption that the main anode circuits of both tubes are not functioning.

Let it be assumed that the first half wave that arrives has a direction such that the voltage inducted in the secondary Winding of transformer T has the direction assumed as positive and indicated by the arrow in full lines, which means, that the induced secondary Voltage will be aiding the biasing potential between Z and B. The values of the respective voltages are so chosen that the sum of these two voltages will be greater than the control gap breakdown voltage; the tube L1 will therefore be lit by the action of the total potential impressed thereupon.

During the reverse (or negative) half wave the tube may be extinguished or may remain lit. This depends on the value of the biasing potential, the magnitude of the induced voltage, the time constant of the circuit and the frequency of the alternating current.

For low frequencies and a small time constant, the tube will become extinguished and will then relight during the following positive half Wave, as explained above.

For higher frequencies, a greater time constant or a biasing potential higher than the control gap sustaining voltage, tube L1 will remain lit also during the negative half Wave.

Whether the control gap of tube L1 remains permanently lit during the duration of the signal or not, has no influence on the operation of the system, as will be explained later.

During the negative half wave the voltage induced in the secondary winding of T has a direction as indicated by the arrow in dotted lines. This voltage causes a current to flow in a closed circuit, comprising the secondary winding of T.

the rectifier R and the resistance 11 shunted by condenser C1. In this way a potential difference is created across resistance n which is opposed to the normal biasing potential between the points Z and C and which is of such a magnitude that the resultant voltage across electrodes c1 and e2 of L2 falls below the control gap sustaining voltage. The tube L2 is consequently extinguished.

Due to the storage action of condenser C1 the opposing voltage across 11 does not have suificient time to fall to zero during the positive half wave of the signaling current, so that tube L2 will remain extinguished as long as the signaling current is applied.

After having thus considered the action of the signaling current upon the control gaps of the tubes, the operation of the tubes with the anode circuits closed will now be described.

In the state of rest, tube L2 is lit and a current flows through resistance 1'4 in series with the anode A of tube L2. Condenser C2 is charged, point D being effectively grounded and point E being brought to a potential Vy equal to the main gap sustaining voltage.

When the signaling current is applied, tube L1 will be lit during the positive half wave, thereby establishing a current through its anode in series with relay Sr, which operates and closes its front contact. By the flow of anode current point D is now suddenly raised to a potential equal to Vy, with the result that condenser C2 discharges. The discharge current increases the drop of potential across resistance n, which in turn causes the potential on the anode of tube L2 to fall below the value of the main gap sustaining voltage, thereby interrupting the main gap current of this tube.

During the first following negative half wave, the control gap of tube L2 is also extinguished, as previously explained, whereafter tube L2 remains extinguished until the signal ceases.

The main gap of tube L1 remains lit and relay Sr remains operated as long as the signal is applied. The condenser C2 is now charged in the opposite direction, point E- being connected to ground and point D having a potential Vy.

As soon as the signaling current is removed, the opposing voltage across 11 disappears, and tube L2 will again be lit. When the anode circuit of L2 is closed, the potential of point I] is raised to the value Vy, causing condenser C2 to discharge in the opposite direction of the first time. The increase of current through the winding of relay S1- results in a drop of voltage on the anode of tube L1, causing the tube to become extinguished. Relay Sr falls oil, and the circuit has now reverted to its original state of rest.

It can be understood from the preceding description, that one pulse, consisting of a certain number of cycles of alternating current, results in the alternate lighting and extinction of the two tubes and in the operation of relay Sr during the entire presence of the signaling current.

Each subsequent pulse is received in exactly the same manner as explained above.

If, therefore, the incoming alternating current, which constitutes the carrier current, is interrupted (or modulated) a various number of times, the number of interruptions (or modulation fre quency), characterising the signal to be transmitted, will be reproduced by the stepping relay S1.

The arrangement shown in Fig. 2 differs from the arrangement of Fig. l in that the cold-cathode tube L1 is provided with an exterior electrode H. This modified construction results in a certain degree of simplification, only one biasing potential being now required.

It is well-known that the exterior electrode acts a regulator of the main gap breakdown voltage of the tube, while the corresponding sustaining voltage is not influenced. The arrangement in Fig. 2 is such that the arrival of the first positive half wave on the electrode H causes the breakdown of the main gap and lights the tube.

Except for the modification applied to tube L1 the arrangement of Fig. 2 functions in the same manner as that of Fig. 1.

Both the previous arrangements may suffer, however, from a somewhat theoretical imperfection, in that the reproduction of the received pulses may be subject to a slight distortion. This is due to the fact that tube L1 is lit (and relay Sr operated), only when the induced voltage in the secondary winding of transformer T reaches a predetermined value and direction. There is therefore, in principle, a variable lapse of time between the arrival of the signal and the operation of relay Sr. In practice this small distortion does not impair the satisfactory operation of the system, provided the frequency of the alternating current which is used lies above a certain figure, for instance, to cycles per second.

Both the previously described schemes give a certain distortion due to the delay in relighting tube L2 after the disappearance of the signaling current. This delay, which is occasioned by the gradual discharge of condenser C1, is constant and may easily be compensated for, by means of changing the adjustment of the stepping relay Sr, in order to make this relay slightly slower in coming up.

The scheme shown in Fig. 8 shows a circuit arrangement which provides a substantially distortionless reproduction of the signals. This result has been obtained by the introduction of the following principal alterations of the foregoing circuits.

(a) Each half wave is utilized on the control electrode of tube L1 by means of a full-wave rectifier;

(b) The unavoidable delay in the relighting of tube L2 at the end of the pulse is compensated for by a corresponding delay in the lighting of tube L1 at the beginning of the pulse;

(0) The anodic distortion is eliminated by introducing a polarized relay with two windings, one winding being inserted in each of the anode circuits.

It will be seen from Fig. 3 that the secondary winding of transformer T is separated into two windings, each of which is associated with a fullwave rectifier bridge R1, R2, respectively. The output points I and 2 of each of these rectifiers are connected in series with the biasing potentials of the control electrodes 61 and e2, of the two cold-cathode tubes. The two cathodes 62 of both tubes are connected to the negative pole of the battery.

The biasing potentials are adjusted in the same way as explained in the description of Fig. l, i. e. during the absence of the signal, tube L1 is extinguished and tube L2 is lit. The purpose of condenser C2 is to prevent the rectified potential produced across points I and 2 of R2 from reaching zero too rapidly. In this way it is assured that tube L2 will not be relit as long as the signaling current persists. A further consequence of the presence of condenser 02 is, that the relighting of tube L2 at the end of each si naling pulse is delayed.

This delay is compensated for by creating artificially a delay in lighting tube L1 at the beginning of each pulse. To this elfect a condenser C3 has been added. When a pulse arrives, condenser C3 is charged in series with resistance 7'3, thus delaying the rectified potential component produced on electrode c1 of tube L1, in reaching its full value. Condenser C3 is preferably made variable, in order to facilitate the adjustment of the system.

Condenser C has the same function as explained above in connection with Fig. 1, i. e. its alternate charge and discharge results in the extinction of tube L1 at the end of the pulse and the extinction of tube L2 at the beginning of the subsequent impulse.

The polarized relay Sr' has one operating winding inserted in each of the anode circuits of L1 and L2. The purpose of this arrangement is to eliminate possible sources of distortion, due to the time of operation of this relay.

Fig. 4 shows the application of an additional arrangement to the circuit of Fig. 3, as an impulse corrector. The basic idea underlying this application is the introduction of an artificial means of distortion in the anode circuits. It will be seen from Fig. 4 that two resistances rs and T6 are inserted in series with the windings of relay Sr and that a, high resistance potentiometer P1 is bridged across the two anode leads to Sr. The sliding contact of potentiometer P1 is grounded via a resistance n.

The purpose of this combination of P1 and rv is to vary the value of the anode current flowing through each winding of Sr, thereby varying also the time of operation and release of the relay.

By this simple means the impulse ratio of the impulses reproduced by relay Sr can be varied within any desired limits.

The arrangement shown in Fig. 5 represents a practical application of the invention to a telephone system or similar system for the establishing of connections in the form of a dial impulse receiving device. The incoming line MM terminates in the primary winding of a transformer T, connected in series with a capacity C1 and a self-inductance 11, adjusted to resonance with i the signaling frequency used. In order to reduce the load on the signaling line due to the inductance of the primary winding of the transformer, the secondary winding of the transformer is preferably shunted by a condenser C2, so designed that resonance is obtained.

The two cold-cathode tubes L1 and L2 are connected in a manner similar to that shown in Fig. 1, with difierent biasing potentials on the two control electrodes. In order to obtain better working limits, the different biasing potentials are stabilized by means of a third cold-cathode tube L, of the same type as L1 and L2. The function of a cold-cathode tube as stabilizer is due to the fact that the potential across the discharge therein varies little, irrespective of current changes. This is well known in the art and therefore it will not be necessary to explain it in detail. It is thought to be sufficient to state that the potential difierence between points Z" and C corresponds to the main gap sustaining voltage, which is greater than the control gap breakdown voltage of tube L2, while the potential difi'erence between points B" and C" corresponds to the control gap sustaining voltage, and is consequent- 1y smaller than the control gap breakdown volta In the state of rest, therefore, provided only that relay H- be operated, tube L2 will light, whereas tube L1 is extinguished.

It will be noticed from Fig. 5 that the cathode circuit of tube L2 is normally not closed. This is done in order to prevent the continuous lighting of tube L2. On the receipt of a signal, tube L1 will be lit, as previously explained, relay Sr and subsequently relay H1 will operate due to closure of Sr, after which the cathode circuit of tube L2 is closed. Relay Hr is a slow releasing relay and will remain operated during the reception of the pulses belonging to the same signal (or digit).

The biasing potential on the electrode er of tube L1 is imposed thereupon via a very high resistance T2, in order to permit the use of one stabilizer tube L common to a plurality of impulse receiving devices.

The anodes of tubes L1 and L2 are connected to the stepping relay Sr in series with resistance 1'5 andre, which serve to reduce the anode current to a minimum. An impulse corrector, comprising a potentiometer P1 and a resistance 1'': is connected in parallel to relay S1, and this corrector functions in the same way as explained above in connection with Fig. 4.

The method of operation of the arrangement shown in Fig. 5 is briefly as follows:

When the first positive half wave of the first pulse arrives, tube L1 is lit, and relays Sr and H1 operate. Tube L2 remains extinguished.

After the disappearance of the first pulse, the original bias on the electrode 61 of tube L2 is applied and this tube is lit. As explained above, this results in the extinction of tube L1 and the release of relay S1.

The next pulse will light tube L1 and extinguish tube L2. Relay Sr will again operate.

Each subsequent pulse is received in the same manner.

After the last pulse tube L2 remains lit until relay Hr releases, after which the circuit reverts to its original state of rest, until signal current is again received from line M, M.

What is claimed is:

1. System for reception of wired carrier currents including transformer means for collecting said carrier currents from the line, two cold cathode tubes connected so as to be fed with said currents from said transformer means, means for keeping the first tube lighted under no-signal conditions including biasing potentials applied to the control electrodes of said tube, means for extinguishing said first tube when a signal is received including bias changing means connected to the control electrodes of said tube, means for lighting the second tube when a signal is received and including means for changing the control bias applied to said second tube, and a polarized relay with two windings, each of which is inserted in the anode circuit of one of the two cold-cathode tubes, whereby incoming current pulses cause the reversal of lighting of the two tubes and the actuation of said relay means.

2. System according to claim 1, in which the secondary winding of the transformer consists of two separate windings, each winding being connected to the input terminals of a separate bridge rectifier, of which the output terminals are connected in series with the biasing potentials of the two cold-cathode tubes so as to oppose the biasing potential of said first tube and to aid the biasing potential of said second tube.

3. System according to claim 1 in which the secondary winding of the transformer consists of two separate windings, each winding being connected to the input terminals of a separate bridge rectifier, of which the output terminals are connected in series with the biasing potentials of the two cold-cathode tubes in such a manner that the first half wave of the incoming carrier current pulse will light the second tube and extinguish the first tube, and also having another condenser connected in shunt tothe control anode of said second cold-cathode tube, to delay the lighting of said second tube by the charging time of said condenser.

4. A system according to claim 1, and also including a variable potentiometer connected in shunt to the anodes of the two cold-cathode tubes, for the purpose of adjusting thereby the time of operation and release of said polarized relay.

5. A system according to claim 1, also including a slow releasing relay controlling the cathode circuit of said first tube, and responsive to the operation of said polar relay to close said cathode circuit.

6. System according to claim 1, including means for causing the potential induced in the secondary winding of the transformer by the incoming carrier current to be of such a magnitude, that the arithmetical sum of the peak of said potential and the biasing potential of the second cold-cathode tube is greater than the control gap breakdown voltage of said second tube, thus causing the lighting of said second tube during the first transformer secondary half wave having a potential of the same direction as the biasing potential of the first tube, and thereby establishing current through said relay means.

'7. System according to claim 1, including a source of biasing potential for applying a bias to the control anodes of each of said two cold-cathode tubes, the biasing potential of the first tube being greater, and of the second tube less than the tube control gap breakdown voltage.

8. System according to claim '7, in which the second of the two cold-cathode tubes is provided with an exterior electrode connected to the secondary winding of the transformer, and said tubes are connected to a common source of biasing potential.

9, System for reception of wired carrier currents including transformer means for collecting said carrier currents from the line, two coldcathode tubes, means for keeping the first tube lighted under no-signal conditions, an ohmic resistance and shunting condenser connected in series with one transformer secondary lead and a non-linear resistance connected also in series with the transformer secondary and said ohmic resistance, in which the transformer secondary negative half waves having a potential opposing the bias of the second tube cause a current to flow in a closed circuit, comprising the secondary winding of the transformer, the ohmic resistance shunted by the condenser and the non-linear resistance, the arrangement being such that said ohmic resistance is also inserted in series with the biasing potential of the first cold-cathode tube, and that the potential created across said ohmic resistance by the secondary potential is opposite in direction to the biasing potential of the first tube, and of such a magnitude that the resulting voltage across the electrodes of the first tube is smaller than the tube control gap sustaining voltage, means for lighting the second tube when a signal is received and relay means in the anode circuit of at least one tube, whereby incoming current pulses cause the reversal of lighting of the two tubes and the actuation of said relay means.

10. System according to claim 9 wherein said relay means comprise a condenser connected between the anodes of the two tubes and a resistance and relay connected in series with each other and in shunt with said condenser, and the anode feed potential is connected to the common terminal of said relay and resistance, whereby the alternate extinction of the main gap of the two cold cathode tubes is under control of the circuit comprising a combination of relay, a resistance and a condenser, the arrangement being such that the alternate charge and discharge of said anode condenser causes alternately the anode potential of the two tubes to be reduced to a value smaller than the main gap sustaining voltage.

LUCIEN A. B. CABES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,932,606 Schramm Oct. 31, 1933 1,964,110 Demarest June 26, 1934 2,022,030 Dimond Nov. 26, 1935 2,104,142 Swart Jan. 4, 1938 2,214,572 Bernstein Sept. 10, 1940 Certificate of Correction Patent No. 2,474,220 June 28, 1949 LUOIEN A. B. OABES It is hereby certified that errors appear in the above numbered patent requiring correction as follows:

In the grant, line 15, strike out the words of seventeen years; same line, after grant insert until July 11, 1.961; in the heading to the printed specification, line 8, before 10 Claims, insert the following-Section 1, Public Law 690, August 8, 1946. Patent expires July 11 1961;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 4th day of July, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommissioner of Patents.

Certificate of Correction Patent N 0. 2,474,220 June 28, 1949 LUCIEN A. B. CABES It is hereby certified that errors appear in the above numbered patent requiring correction as follows:

In the grant, line 15, strike out the words of seventeen years; same line, after grant insert until July 11 1961 in the heading to the printed specification, line 8, before 10 Claims, insert the following-Section 1, Public Law 690, August 8, 1946. Patent expires July 11, 1.961;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 4th day of July, A. D. 1950.

THOMAS F. MURPHY,

Assistant C'ommz'ssz'oner of Patents. 

